Incandescent and halogen type lamps have been widely used in various conventional lighting devices for the projection of light onto a surface for illumination and for general illumination purposes. Such lamps depend on the heating of a tungsten wire filament to a high temperature and therefore emit light. These lamps are not energy efficient and they generate excessive heat.
Illuminating light sources such as metal halide arc lamps, gas discharge lamps, fluorescent lamps and halogen light bulbs, as examples, have been widely used in various conventional lighting devices for the projection of light onto a surface for illumination. Such light sources are used in architectural, theatrical and stage lighting systems as well as in industrial applications for lighting surfaces, scenery, an object, or a person. These light sources are also used to project a sharp image of a gobo, shutter cut, or pattern onto a surface when such items are placed at the gate aperture of lighting devices somewhere between the light source and a lens lighting system.
These image projection and lighting systems are typically called ellipsoidals. Conventional lighting systems comprise an ellipsoidal reflector used with a single high-intensity lamp, an imaging gate, and light collection lenses, including focusing lenses and collimating lenses. A single ellipsoidal reflector is used because it enhances light collection in the most efficient configuration known in the art of light projection. By definition, an ellipse has two focal points. The curve of an ellipsoidal reflector is matched with the light source to produce an exact focused secondary image of the light source at the same distance at which it is located from the reflector at the opposite end. When a light source is placed at the primary focal point of the reflector, the ellipsoidal reflector reflects or redirects, the light to the secondary focal point in front of the reflector. Multi-facets on the inside surface of the ellipsoidal reflector project the light beams to the secondary focal point.
Conventional light sources have shortcomings. They generate a large amount of heat and so consume a large amount of energy, with the result that lamp life is short. In addition, lighting systems that use the conventional light sources suffer from the excess amount of heat that is transferred to the exterior of the fixture housing. Likewise, the use of the incandescent filament lamps and arc lamps in conventional ellipsoidal projection lighting systems transfer a high degree of heat to the fixtures. The primary reason for this heat loss is that a major part of the light energy is in fact wasted as infrared heat energy. The use of cold mirror coated reflectors has helped somewhat, but these fixtures continue to have low energy efficiency. An additional problem with conventional light sources is that they have low resistance to vibration.
An alternate light source is the light emitting diode (LED). Advancements have been made in LED technology and in the overall use of LEDs. LEDs have several different characteristics that set them apart from conventional light emitting technology. As one example, an LED used in place of a conventional light source will produce a cooler, longer running, and more energy efficient lighting fixture. A disadvantage of LEDs when compared to incandescent and halogen lamps is their relatively low illumination intensity. A basic characteristic of LEDs that sets them apart from conventional light emitting technology is that while conventional lamps radiate light into the surrounding hemisphere with relatively equal intensity in all directions, light emitting diode lamps with their substantially planar luminescent elements radiate high intensity light primarily in the forward direction resulting in only minimal quantities of light energy radiated to the sides. It is to be noted, however, that LEDs are presently manufactured with integral lenses molded into the diode housings just in front of the diode chip. Even with the lenses, however, LEDs are available only with some degree of beam spread, or angle. Beam spreads of a LED, shown in FIG. 1 herein for purposes of exposition only, vary according to the manufacturer generally between approximately 5 and 70 degrees. Despite there being some degree of beam spread, LEDs are much more centered than conventional lamp technology. For purposes of clarity, FIG. 2 shows a straight line representing the virtual center of a typical LED beam.
The solid state design of LEDs allows them to be more durable and robust, and lets them withstand shock, vibration, frequent power cycling, and extreme temperatures. LEDs have an average usable life of typically 100,000 hours or more when they are operated within their electrical specifications. In comparison, incandescent filament lamps generate high-intensity light for only a short time, typically a few hundred hours, and are very susceptible to damage from both shock and vibration.
Red, green, and blue (RGB) LEDs are known in the art. It is noted that color gel filters used with conventional light source technology are not necessary in diode technology because RGB LEDs are capable of serving as a full color spectrum generating light source. The primary colors red, green, and blue of RGB LEDs can be mixed to produce the secondary colors cyan, yellow, magenta (CYM), and also white light. Mixing green and blue gives cyan, as is known in the art of colors. Likewise as is known in the art, mixing green and red gives yellow. Mixing red and blue gives magenta. Mixing red, green, and blue together results in white. Advances in light-emitting diode technology include the development of multi-chip and multi-LED arrays, which have led to brighter LEDs available in different colors. LEDs are available in both visible colors and infrared. In addition to red, yellow, and amber/orange, which were the first available colors, LEDs are also available in green, blue, and even white light. Clearly, for many applications, light-emitting diodes can compete directly with incandescent filament light sources.
While incandescent filament lamps give off the full spectrum of light, LEDs can emit focused discrete beams of color at a variety of different angles. Color efficiency in LEDs is much better than it is for incandescent filament lamps. In order to get color from an incandescent filament lamp, a specific color gel or filter in that particular color spectrum has to be used. This can waste 90 percent and more of the incandescent filament lamp's light energy. In comparison, LEDs deliver 100% of their energy as light and give a more intense colored light. This efficiency also gives LEDs the advantage of white light as well.
LED lamps have been considered for many lighting devices because of their long life, high luminous efficiency, and intrinsic colors. However, their use has been limited to low intensity devices because individually, they emit only small quantities of light energy. It has not been possible to efficiently combine a plurality of LED lamps into a single lighting device comprising a number of LEDs of limited size together capable of emitting a concentrated light beam meeting specific intensity, beam spread, power consumption, and size requirements that is related to large scale lighting arts such as architectural displays, and theatrical and stage productions.